i picked up a NES and some games today. 4 of the games still have their cardboard boxes so i figured that i would see how much they sell for on ebay. one was Zelda II: the adventure of link. while checking the price i noticed that not all of the copies are gold like mine. this got me wondering why some are gold and some are not? does anyone know anything about this?

below is a picture of the boxed games. these boxes are in pretty damn good shape for how old they are.

its funny because people say there are gray carts of zelda II but in my gaming lifetime ive never seen one. of course they apparently do exist so my guess is nintendo made the gray ones after the gold ones ran out or they just wanted to make it a standard gray, standard cart for cost measures. i think there are a lot more gold carts out there though.